<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>

    <style>
      .arrow-btn {
        padding: 10px;
        width: 15px;
        height: 15px;
        border: 1px solid #ddd;
        margin: 20px;
      }

      .arrow-btn::after{
        content: '';
        display: block;
        height: 15px;
        border-top: 1px solid #333;
        border-left: 1px solid #333;
        transition: transform .7s;
      }

      .arrow-up::after{ 
        transform: rotate(45deg);
      }

      .arrow-up:hover::after{ 
        transform: rotate(-135deg);
      }

      .arrow-down::after{ 
        transform: rotate(-135deg);
      }

      .arrow-down:hover::after{ 
        transform: rotate(45deg);
      }
    </style>
  </head>
  <body>
    <div class="arrow-btn arrow-up"></div>
    <div class="arrow-btn arrow-down"></div>
  </body>
</html>
